Lifting the load with the help of a movable block to a height of 2 m perform work 2940 J

Lifting the load with the help of a movable block to a height of 2 m perform work 2940 J, determine the weight of the load if the efficiency of the mechanism is 80%.

Given: m (lifting height) = 2 m; Az (perfect (useful) work) = 2940 J (there is no gain in work); η (efficiency of the used mechanism) = 80% (0.8).

Constants: g (acceleration due to gravity) ≈ 9.8 m / s2.

The mass of the lifted load can be expressed from the formula: η = Ap / Az = m * g * h / Az, whence m = η * Az / (g * h).

Let’s calculate: m = 0.8 * 2940 / (9.8 * 2) = 120 kg.

Answer: The weight of the lifted load is 120 kilograms.